Sub-channel and power allocation method and apparatus for multicast transmission using an orthogonal frequency division multiple access scheme

Abstract

A method and apparatus are described including allocating one of a plurality of sub-channels to one of a plurality of multicast group clients for a multicast session and performing bit-loading for the allocated sub-channel, wherein said performing act further includes finding one of the plurality of multicast group clients having a lowest received bit rate, finding one of the plurality of sub-channels needing a lowest power to transmit one more bit to the one of the plurality of multicast group clients having the lowest received bit rate, comparing the needed power to a residual power, adding one more transmission bit to the sub-channel if the needed power is not greater than the residual power and updating a multicast rate, the residual power and the power need to transmit one more bit if the needed power is not greater than the residual power.

Description

FIELD OF THE INVENTION[0001]The invention relates to wireless multicast communications generally and, in particular, to resource allocation for multiple multicast sessions and to sub-channel and power allocations for wireless multicast communications using an orthogonal frequency division multiple access (OFDMA) scheme for any given multicast session.BACKGROUND OF THE INVENTION[0002]In multicast / broadcast applications, data are transmitted from a server or base station (BS) to multiple receivers over wired and / or wireless networks. Herein, a “ / ” is used to indicate alternative names for the same or similar components. A multicast system as used herein is a system in which a server transmits the same data to multiple receivers simultaneously, where the receivers form a subset of all the receivers up to and including all of the receivers. A broadcast system is a system in which a server transmits the same data to all of the receivers simultaneously. That is, a multicast system by defi...

AI Technical Summary

Benefits of technology

[0007]OFDMA access technology is expected to play an important role in the next generation wireless communication systems. The next generation wireless communication systems are being designed for high quality multimedia support such as mobile audio / video multicast / broadcast. In a multicast / broadcast system, a group of users need to receive the same content at the same bit rate. In an OFDMA system, when a certain number of sub-channels are allocated to a multicast / broadcast application, the channel gains for each sub-channel to different users in the multicast group are different. If each member of the multicast group is required to receive data transmitted by all the sub-channels reliably, the transmission data rate on a sub-channel has to accommodate the user that has the worst channel gain on that sub-channel. To improve bandwidth efficiency, the present invention divides the users in a multicast group into subgroups based on their sub-channel gains. The method of the present invention then allocates sub-channels to each subgroup. A bit loading method for power allocation on each sub-channel is also described.

[0008]The present invention maximizes the multicast rate by performing resource allocation with a power constraint as well as considering fairness among users. A two-step approach is used on the problem. The two-step approach separates sub-channel allocation and power allocation. A greedy method is described for sub-channel allocation and a bit loading method is described and used to allocate power to sub-channels.

Problems solved by technology

Conventional multicast systems suffer from bad channel conditions.

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